JPWO2006004098A1 - Electrolyte membrane and fuel cell using the electrolyte membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be used for electrochemical device applications such as a polymer electrolyte fuel cell, having high proton conductivity, excellent in permeation-preventing performance of methanol when used as a DMFC, and durable when operated as a fuel cell. Providing excellent and inexpensive electrolyte membranes. SOLUTION: (a) A compound having a carbon-carbon double bond and a sulfonic acid group polymerizable in one molecule or a salt thereof, and (b) a (meth) acrylamide derivative represented by a specific structural formula are essential. An electrolyte membrane comprising a crosslinked electrolyte polymer as a constituent monomer.

Description

  The present invention relates to an electrolyte membrane, and the electrolyte membrane is excellent for electrochemical devices, particularly for fuel cells, and more specifically for direct alcohol fuel cells.

  As global environmental protection activities become more active, so-called greenhouse gas and NOx emission prevention is strongly screamed. In order to reduce the total emission amount of these gases, it is considered that practical application of a fuel cell system for automobiles is very effective.

  A polymer electrolyte fuel cell (PEFC), which is a type of electrochemical device using a polymer electrolyte membrane, has excellent features such as low temperature operation, high output density, and low environmental impact. . Among them, PEFC, which is a methanol fuel, can be supplied as a liquid fuel in the same way as gasoline, and thus is considered promising as a power source for electric vehicles and a power source for portable devices.

  When using methanol as a fuel, PEFC is divided into a reformed methanol type that uses a reformer to convert methanol into a hydrogen-based gas, and a direct methanol type that uses methanol directly without using a reformer (DMFC, It is divided into two types, Direct Methanol Polymer Fuel Cell). Since DMFC does not require a reformer, it has great advantages such as being able to reduce weight, and its practical use is expected.

  However, when an electrolyte membrane for DMFC is a perfluoroalkylsulfonic acid membrane that is an electrolyte membrane for PEFC using conventional hydrogen as a fuel, such as a Nafion (registered trademark) membrane manufactured by Du Pont, Since methanol permeates the membrane, there is a problem that the electromotive force decreases. Furthermore, these electrolyte membranes also have an economic problem that they are very expensive.

  As means for solving the above problem, Patent Document 1 proposes an electrolyte membrane in which a porous base material such as polyimide, crosslinked polyethylene, etc., which is inexpensive and hardly deformed by external force, is filled with a polymer having proton conductivity. Has been made. However, since the electrolyte membrane includes a step of subjecting the base material to plasma irradiation and graft polymerization of the polymer, there is a problem of an increase in manufacturing equipment cost. In addition, the durability when continuously operating as a fuel cell was not sufficient.

Furthermore, Patent Document 2 discloses an electrolyte membrane in which a first polymer having proton conductivity is filled in pores of a porous base material that does not substantially swell with an organic solvent containing methanol and water. An electrolyte membrane has been proposed in which the first polymer is a polymer derived from 2-acrylamido-2-methylpropanoic acid. However, the durability of the electrolyte membrane described in this patent document is still insufficient.
JP 2002-83612 A (pages 1-7, 9) International Publication No. 03/075385 Pamphlet

  The object of the present invention is to solve these problems, that is, it can be used for electrochemical device applications such as polymer electrolyte fuel cells, has high proton conductivity, and has excellent methanol permeation blocking performance when used as a DMFC, Another object is to provide an inexpensive electrolyte membrane that is excellent in durability when operated as a fuel cell.

  As a result of intensive studies, the present inventors have identified 2-acrylamido-2-methylpropanesulfonic acid and / or 2-methacrylamideamido-2-methylpropanesulfonic acid (hereinafter “acrylic and / or methacrylic” as “(meth)”. As an introduction method of the crosslinked structure, N, N′-ethylenebis (meth) is used as an electrolyte membrane containing a crosslinked electrolyte polymer obtained by polymerizing a monomer having a sulfonic acid group or a salt thereof as a main component. Identification of acrylamide, N, N′-propylene bis (meth) acrylamide, N, N′-butylene bis (meth) acrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, bisacryloylpiperazine, etc. One or more models selected from among (meth) acrylamide derivatives of structure When obtained by copolymerizing mer, proton conductive electrolyte membrane is excellent in permeation preventing performance of methanol, and found that durability is good, and have completed the present invention.

R₁、R₃ は、水素またはメチル基
R₂は、鎖状または環構造の一部を構成するアルキレン基であって、鎖状の場合は炭素数が２以上で、環構造の一部の場合は炭素数が１以上である。
R₄、R₅ は、水素、アルキル基または環構造の一部を構成するアルキレン基
を、必須構成モノマーとする架橋電解質ポリマーを含有することを特徴とする電解質膜である。That is, the present invention relates to (a) a compound having a carbon-carbon double bond polymerizable in one molecule and a sulfonic acid group or a salt thereof, and (b) (meth) acrylamide represented by the following structural formula (1). Derivative

R ₁ and R ₃ are hydrogen or methyl group
R ₂ is an alkylene group constituting a part of a chain or ring structure, and in the case of a chain, has 2 or more carbon atoms, and in the case of a part of the ring structure, R ₂ has 1 or more carbon atoms.
R ₄ and R ₅ are electrolyte membranes containing a crosslinked electrolyte polymer having hydrogen, an alkyl group or an alkylene group constituting a part of the ring structure as an essential constituent monomer.

Further, as monomer (b), N, N′-ethylenebis (meth) acrylamide, N, N′-propylenebis (meth) acrylamide, N, N′-butylenebis (meth) acrylamide, 1,3,5-tri Acryloylhexahydro-1,3,5-triazine and / or 1,3,5-trimethacryloylhexahydro-1,3,5-triazine (hereinafter referred to as “acryloyl and / or methacryloyl”, “(meth) acryloyl”) And one or more compounds selected from bis (meth) acryloylpiperazine.
Further, 2- (meth) acrylamido-2-methylpropanesulfonic acid or a salt thereof is used as the monomer (a), and the monomers (a) and (b) of all monomers constituting the crosslinked electrolyte polymer are used. The electrolyte membrane is characterized in that the ratio is 25 to 99.9% by mass and 0.1 to 75% by mass, respectively.
Further, the present invention is an electrolyte membrane characterized in that the crosslinked electrolyte polymer is filled in pores of a porous substrate, and further, the electrolyte membrane constitutes (1) a crosslinked electrolyte polymer And a solution or dispersion thereof filled in the pores of the porous substrate, and (2) a production method comprising a step of polymerizing and crosslinking the filled monomer.
The present invention also relates to a fuel cell incorporating the above electrolyte membrane.

  The electrolyte membrane of the present invention has improved durability by containing a crosslinked electrolyte polymer having a specific composition. Further, since it is an electrolyte membrane excellent in proton conductivity and methanol permeation blocking performance, it can be suitably used as an electrolyte for a polymer electrolyte fuel cell, particularly a direct methanol polymer electrolyte fuel cell.

Hereinafter, the present invention will be described in detail.
The electrolyte membrane of the present invention comprises (a) a compound having a carbon-carbon double bond polymerizable in one molecule and a sulfonic acid group or a salt thereof, and (b) (meth) acrylamide represented by the formula (1). It contains a crosslinked electrolyte polymer obtained by copolymerizing a monomer mixture having a derivative as an essential constituent monomer (hereinafter referred to as “polymer precursor”).

Here, the ratio of the essential constituent monomers (a) and (b) to the total monomers constituting the crosslinked electrolyte polymer is preferably 25 to 99.9 mass% and 0.1 to 75 mass%, respectively. . When the monomer (a) is lower than the lower limit of the above range, the proton conductivity of the obtained electrolyte membrane tends to be low, the output per area of the obtained electrolyte membrane tends to be low, and the incorporated fuel cell becomes large. . On the other hand, if it is higher than the upper limit of the above range, neither methanol permeation-preventing property nor durability is likely to be lowered, which is not preferable.
When the monomer (b) is lower than the lower limit of the range, the resulting electrolyte membrane methanol permeation-preventing property and durability are likely to be lowered, whereas when it is higher than the upper limit of the range, the proton conductivity is likely to be lowered. Therefore, neither is preferable.
More preferable ranges are 40 to 90% by mass of monomer (a) and 10 to 60% by mass of monomer (b).

    The monomer (a) constituting the crosslinked electrolyte polymer used in the electrolyte membrane of the present invention is a compound having a polymerizable carbon-carbon double bond and a sulfonic acid group in one molecule or a salt thereof, and is not particularly limited. 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, allylsulfonic acid and / or methallylsulfonic acid “Allyl and / or methallyl” is referred to as “(meth) allyl”.), Monomers such as vinyl sulfone, or salts thereof. These may be used alone or copolymerized, but 2- (meth) acrylamido-2-methylpropanesulfonic acid or a salt thereof is particularly preferable in terms of good polymerizability. Moreover, since vinyl sulfonic acid has the highest sulfonic acid content per molecular weight, it is preferable to use it as a copolymerization component because proton conductivity of the electrolyte membrane is improved.

  The monomer (b) constituting the crosslinked electrolyte polymer used in the electrolyte membrane of the present invention is a (meth) acrylamide derivative represented by the above formula (1), and specific preferred compounds include N, N′— Ethylene bis (meth) acrylamide, N, N′-propylene bis (meth) acrylamide, N, N′-butylene bis (meth) acrylamide, 1,3,5-tri (meth) acryloylhexahydro-1,3,5- It is a compound selected from triazine and bis (meth) acryloylpiperazine, and these may be used alone or copolymerized, but they are highly soluble in water and more durable. N, N′-ethylenebis (meth) acrylamide is particularly preferable in terms of improvement.

The monomer constituting the crosslinked electrolyte polymer used in the electrolyte membrane of the present invention contains monomers (a) and (b) as essential components, but other monomers can be used in combination as necessary. .
The monomer is not particularly limited as long as it is copolymerizable with the monomers (a) and (b). For example, as a water-soluble monomer, (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, Acidic monomers such as crotonic acid, itaconic acid, vinylphosphonic acid, acidic phosphoric acid group-containing (meth) acrylate and salts thereof; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl acrylate and / or 2- Hydroxyethyl methacrylate (hereinafter, “acrylate and / or methacrylate” is referred to as “(meth) acrylate”), 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, N -Vinyl pylori Monomers such as N, N-vinylacetamide; basic monomers such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide And quaternized compounds thereof can be specifically mentioned.
Acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, vinyl acetate, and vinyl propionate are also used to adjust the water absorption of the polymer filled in the pores. Hydrophobic monomers such as can also be used.

In the crosslinked electrolyte polymer used in the electrolyte membrane of the present invention, as a method for introducing a crosslinked structure, it is preferable to have a crosslinked structure derived from the essential constituent monomer (b).
As a method for introducing a crosslinked structure derived from the monomer (b), the polymer precursor is filled into the pores of the porous substrate and then subjected to a polymerization reaction, or simultaneously with the polymerization reaction to obtain a polymer, the monomer (b ) Or a method of polymerizing a polymer precursor in advance and filling the polymer solution into the pores of the porous substrate, followed by a crosslinking reaction. Among these methods, in the method of filling after the polymer is first prepared, gelation occurs at the time of polymerization, which makes it impossible to fill, and the yield is poor, and the viscosity of the polymer is higher than the polymer precursor solution. Since it takes time to fill the pores or the filling tends to be insufficient, a method of polymerizing and cross-linking after pre-filling the polymer precursor is preferable.
The crosslinking is preferably promoted by heating or active energy rays such as ultraviolet rays, electron beams, and gamma rays. The conditions are preferably 50 to 150 ° C. for 1 to 120 minutes in the case of heating, and 10 in the case of ultraviolet irradiation. ˜5000 mJ / cm ² is desirable.

In the crosslinked electrolyte polymer used in the electrolyte membrane of the present invention, a crosslinked structure other than the crosslinked structure derived from the essential constituent monomer (b) that is a polyfunctional monomer may be introduced, and the method is not particularly limited and is publicly known. This method can be used.
Specifically, a method of performing a polymerization reaction in combination with a crosslinking agent having two or more polymerizable double bonds, a method of copolymerizing a monomer having a functional group capable of forming a crosslinked structure, a functional group in the polymer A method using a cross-linking agent that has two or more groups in the molecule to react with, a method using self-crosslinking by hydrogen abstraction reaction during polymerization, and irradiating the polymer after polymerization with active energy rays such as ultraviolet rays, electron beams and gamma rays And the like.
Among these methods, a method in which a polymerization reaction is carried out using a crosslinking agent having two or more polymerizable double bonds in combination is preferable because of the ease of introduction of a crosslinked structure. Examples of the crosslinking agent include N, N-methylenebisacrylamide, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, and trimethylolpropane. Di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane diallyl ether, pentaerythritol triallyl ether , Divinylbenzene, bisphenol diacrylate, isocyanuric acid diacrylate, tetraallyloxyethane, triallyl Min, triallyl cyanurate, triallyl isocyanurate, include diallyloxyacetic acetates. A method of copolymerizing a water-soluble monomer having a functional group capable of forming a crosslinked structure is also preferred from the viewpoint of easily increasing the crosslinking density. Examples of such compounds include N-methylol acrylamide, N-methoxymethyl acrylamide, N-butoxymethyl acrylamide, and the like. After radical polymerization of a polymerizable double bond, heating is performed to cause a condensation reaction. It is possible to cause the same crosslinking reaction by crosslinking or heating simultaneously with radical polymerization. These cross-linking agents can be used alone or in combination of two or more as required.
The amount of the copolymerizable crosslinking agent used is 0.01 to 20% by mass, preferably 0.1 to 20% by mass, more preferably 0.1 to 20% by mass with respect to the total mass of unsaturated monomers in the polymer precursor. 10% by mass. If the amount of the crosslinking agent is too small, the uncrosslinked polymer tends to be eluted, and there is a problem that the output decreases within a short time when operated as a fuel cell. If the amount is too large, the crosslinking agent component is difficult to be compatible. Neither is preferred because there is a problem of hindering conduction and reducing battery performance.

As a method for obtaining a crosslinked electrolyte polymer by copolymerizing the polymer precursor used in the electrolyte membrane of the present invention, a known aqueous solution radical polymerization technique can be used. Specific examples include redox-initiated polymerization, heat-initiated polymerization, electron beam-initiated polymerization, and photoinitiated polymerization such as ultraviolet rays.
Examples of the radical polymerization initiator for heat-initiated polymerization and redox-initiated polymerization include the following. Azo compounds such as 2,2′-azobis (2-amidinopropane) dihydrochloride; ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, cumene hydroperoxide, di-t-butylperoxide A peroxide such as oxide; a redox initiator in which the above-mentioned peroxide is combined with a reducing agent such as sulfite, bisulfite, thiosulfate, formamidinesulfinic acid, ascorbic acid; or 2,2′-azobis -Azo radical polymerization initiators such as (2-amidinopropane) dihydrochloride and azobiscyanovaleric acid. These radical polymerization initiators may be used alone or in combination of two or more.
Among these, the peroxide radical polymerization initiator can generate radicals by extracting hydrogen from carbon-hydrogen bonds, so when used in combination with an organic material such as polyolefin as a porous substrate, the surface of the substrate and the filled polymer It is preferable because a chemical bond can be formed between the two.

Among the radical polymerization initiating means, photoinitiated polymerization by ultraviolet rays is desirable in that the polymerization reaction is easily controlled and a desired electrolyte membrane can be obtained with a relatively simple process and high productivity. In the case of further photoinitiating polymerization, the radical photopolymerization initiator is more preferably dissolved or dispersed in advance in the polymer precursor, a solution or dispersion thereof.
Examples of the radical photopolymerization initiator include benzoin, benzyl, acetophenone, benzophenone, quinone, thioxanthone, thioacridone, and derivatives thereof that are generally used for ultraviolet polymerization. Examples of the derivatives include benzoin-based benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; acetophenone-based diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1- ON, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-montolinopropane-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) ) Butanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4- (2-hydroxyethoxy) -phenyl) -2-hydroxydi-2-methyl-1-propane- 1-one; as benzophenone, o-benzoy Methyl benzoate, 4-phenylbenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-Benzoyl-N, N-dimethyl-N- [2- (1-oxy-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium chloride, 4,4′-dimethylamino Examples include benzophenone and 4,4′-diethylaminobenzophenone.

The amount of these photopolymerization initiators used is preferably 0.001 to 1% by mass, more preferably 0.001 to 0.5% by mass, particularly preferably the total mass of unsaturated monomers in the polymer precursor. 0.01 to 0.5% by mass. If the amount of the initiator is too small, there is a problem that the amount of unreacted monomers increases. If the amount is too large, the crosslinking density of the polymer to be formed becomes too low, and the durability when the fuel cell is operated is lowered. Therefore, neither is preferable.
Of these, aromatic ketone radical polymerization initiators such as benzophenone, thioxanthone, quinone, and thioacridone can generate radicals by extracting hydrogen from carbon-hydrogen bonds. When used together, a chemical bond can be formed between the substrate surface and the filled polymer, which is preferable.
The electrolyte membrane of the present invention preferably has a structure in which a crosslinked electrolyte polymer is filled in the pores of the porous substrate.

The porous substrate used in the present invention is preferably a material that does not substantially swell with respect to methanol and water, and it is desirable that there is little or almost no change in area when wetted with water, especially when dry.
Although the area increase rate varies depending on the immersion time and temperature, in the present invention, the area increase rate when immersed in pure water at 25 ° C. for 1 hour is preferably 20% or less at the maximum compared to the time of drying.

The porous substrate used in the present invention preferably has a tensile modulus of 500 to 5000 MPa, more preferably 1000 to 5000 MPa, and preferably has a breaking strength of 50 to 500 MPa, more preferably 100. ~ 500 MPa.
If these ranges are deviated to the lower side, the membrane tends to be deformed by the force of swelling of the filled polymer with methanol or water, and if it deviates to the higher side, the base material becomes too brittle and press molding and battery for electrode joining are performed. The film is liable to crack due to tightening during assembly.

Further, the porous substrate is preferably one having heat resistance against the temperature at which the fuel cell is operated, and one that does not easily extend even when an external force is applied.
Examples of the material having such a property include inorganic materials such as glass or ceramics such as alumina or silica. Examples of organic materials include engineering plastics such as aromatic polyimides, polyolefins that have been made difficult to be deformed such as being stretched against external forces by methods such as radiation irradiation and crosslinking or stretching by adding a crosslinking agent. It is done. These materials may be used alone or in combination by stacking two or more of them.

  Among these porous base materials, those made of stretched polyolefin, cross-linked polyolefin, cross-linked polyolefin after stretching, and polyimides are preferable from the viewpoint of good workability in the filling step and easy availability of the base material.

The porosity of the porous substrate used in the present invention is preferably 5 to 95%, more preferably 5 to 90%, and particularly preferably 20 to 80%. Moreover, it is preferable that an average hole diameter exists in the range of 0.001-100 micrometers, More preferably, it is the range of 0.01-1 micrometer. If the porosity is too small, there are too few proton acidic groups, which are proton conductive groups per area, and the output of the fuel cell will be low.
Furthermore, the thickness of the substrate is preferably 200 μm or less. More preferably, it is 1-150 micrometers, More preferably, it is 5-100 micrometers, Most preferably, it is 5-50 micrometers. If the film thickness is too thin, the film strength decreases and the amount of permeated methanol also increases.

  There is no particular limitation on the method of filling the crosslinked electrolyte polymer in the pores of the porous substrate, and a known method can be used. For example, a method of impregnating a porous substrate with a polymer precursor or a solution or dispersion thereof, and then polymerizing and crosslinking the polymer precursor can be mentioned. At that time, the mixed liquid to be filled may contain a crosslinking agent, a polymerization initiator, a catalyst, a curing agent, a surfactant and the like, if necessary.

When the polymer precursor filled in the pores of the porous substrate has a low viscosity, it can be used for impregnation as it is, but otherwise it is preferably a solution or a dispersion. In particular, a solution with a concentration of 10 to 90% by mass is preferable, and a solution with a concentration of 20 to 70% by mass is more preferable.
In addition, if the components used are insoluble in water, some or all of the water may be replaced with an organic solvent, but when using an organic solvent, remove all the organic solvent before joining the electrodes. An aqueous solution is preferred because it is necessary. The reason for impregnation in the form of a solution in this way is that it is easy to impregnate a porous substrate having pores by dissolving in water or a solvent and using it for impregnation, and that a pre-swelled gel is contained in the pores. This is because when the manufactured electrolyte membrane is made into a fuel cell, water or methanol has an effect of preventing the polymer in the pores from swelling too much and the polymer from falling off.
Further, for the purpose of facilitating the impregnation operation, hydrophilic treatment of the porous substrate, addition of a surfactant to the polymer precursor solution, or ultrasonic irradiation during the impregnation can be performed.

  In addition, it is preferable that a crosslinked electrolyte polymer having proton conductivity is chemically bonded to the surface of the porous substrate, particularly the surface inside the pores. As a means for forming the bond, the polymer precursor to be filled is a radical. In the case of a polymerizable substance, the substrate is preliminarily irradiated with plasma, ultraviolet rays, electron beams, gamma rays, corona discharge, etc. to generate radicals on the surface, and when the filled polymer precursor is polymerized, it is grafted onto the substrate surface. A method that allows polymerization to occur simultaneously, a method that causes graft polymerization to the surface of the substrate and polymerization of the polymer precursor simultaneously by irradiating an electron beam after filling the polymer precursor to the substrate, radical extraction polymerization of hydrogen abstraction type Initiator is blended with polymer precursor, heated, or irradiated with ultraviolet rays to simultaneously graft onto the substrate surface and polymer precursor polymerization The method of causing, methods and the like using a coupling agent. These may be performed alone or a plurality of methods may be used in combination.

  The electrolyte membrane according to the present invention can have excellent proton conductivity by containing a crosslinked electrolyte polymer having a sulfonic acid group. Further, the crosslinked electrolyte polymer is N, N′-ethylenebis (meth) acrylamide, N, N′-propylenebis (meth) acrylamide, N, N′-butylenebis (meth) acrylamide, 1,3,5-tri (meth) ) Since a polyfunctional monomer selected from acryloylhexahydro-1,3,5-triazine and bis (meth) acryloylpiperazine is used as a cross-linking agent, methanol permeability is suppressed, and hydrolysis is performed. It becomes a stable electrolyte polymer. As a result, the electrolyte membrane has excellent durability.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, the scope of the present invention is not limited by these examples. Moreover, the part in an Example and a comparative example shall mean a mass part unless there is particular notice. The proton conductivity, methanol permeability, and durability (forced deterioration test) of the obtained electrolyte membrane were evaluated as follows.

  <Proton conductivity> The conductivity of the swollen sample at 25 ° C was measured. An electrolyte membrane that was swollen by being immersed in pure water for 1 hour was sandwiched between two platinum plates to obtain a measurement sample. Thereafter, AC impedance measurement from 100 Hz to 40 MHz was performed to measure the conductivity. The higher the conductivity, the easier the protons move in the electrolyte membrane, indicating that the fuel cell is excellent.

  <Methanol Permeability> A permeation experiment at 25 ° C. was performed as follows. The electrolyte membrane was sandwiched between glass cells, 10% by mass aqueous methanol solution was placed in one cell, and pure water was placed in the other cell. The amount of methanol penetrating the pure water side was measured over time by gas chromatographic analysis, and the permeation coefficient when it reached a steady state was measured. A lower permeation coefficient indicates that methanol is less likely to pass through the electrolyte membrane and is suitable for fuel cell applications.

  <Durability (Forced Degradation Test)> Durability was evaluated by forced degradation instead of confirming the polymer degradation phenomenon due to hydrolysis in the battery. The electrolyte membrane immersed in pure water was allowed to stand for 6 hours at 121 ° C. and 2 atmospheres. The elution rate of the filled polymer in the electrolyte membrane was determined from the weight change before and after the test. The larger the elution rate, the faster the deterioration when operated as a battery.

(Example 1)
A cross-linked polyethylene film (thickness 16 μm, porosity 38%) was used as the porous substrate. 2-acrylamido-2-methylpropanesulfonic acid 45 parts, N, N′-ethylenebisacrylamide 5 parts, nonionic surfactant 0.5 part, 2-hydroxy-2-methyl-1-phenylpropane-1-one The porous substrate was immersed in an aqueous monomer solution composed of 0.05 part and 50 parts of water, and the aqueous solution was filled into the porous substrate. Next, after pulling up the porous substrate from the solution, ultraviolet rays were irradiated for 2 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores to obtain an electrolyte membrane. Table 1 shows the evaluation results of the obtained film.

(Synthesis Example 1)
A mixed solution of 150 g of acetonitrile and 5 g of acrylic acid chloride was charged into a four-necked flask and stirred while keeping the temperature at 5 ° C. or lower in an ice bath. To this, a mixture of 100 g of acetonitrile and 3.7 g of propylenediamine was added dropwise little by little while keeping the mixture in the flask at 5 ° C. or lower. After completion of dropping, the ice bath was removed and the mixture was stirred at room temperature for 5 hours. The precipitate produced in the reaction solution was removed by filtration, and the filtrate was concentrated to give crystals, which were filtered and dried to obtain N, N′-propylenebisacrylamide.

(Example 2)
An electrolyte membrane was obtained in the same manner as in Example 1 except that N, N′-ethylenebisacrylamide obtained in Synthesis Example 1 was used instead of N, N′-ethylenebisacrylamide in Example 1. Table 1 shows the evaluation results of the obtained film.

(Synthesis Example 2)
A mixed solution of 150 g of acetonitrile and 5 g of acrylic acid chloride was charged into a four-necked flask and stirred while keeping the temperature at 5 ° C. or lower in an ice bath. A mixture of 100 g of acetonitrile and 4.4 g of butylene diamine was added dropwise thereto while keeping the mixture in the flask at 5 ° C. or lower. After completion of dropping, the ice bath was removed and the mixture was stirred at room temperature for 5 hours. The precipitate produced in the reaction solution was removed by filtration, and the filtrate was concentrated to give crystals, which were filtered and dried to obtain N, N′-butylenebisacrylamide.

(Example 3)
An electrolyte membrane was obtained in the same manner as in Example 1 except that N, N′-butylene bisacrylamide obtained in Synthesis Example 2 was used instead of N, N′-ethylenebisacrylamide in Example 1. Table 1 shows the evaluation results of the obtained film.

Example 4
In Example 1, electrolyte was used in the same manner as in Example 1 except that bisacryloylpiperazine was used in place of N, N′-ethylenebisacrylamide, 35 parts of water was added to 35 parts, and 15 parts of dimethyl sulfoxide was newly added. A membrane was obtained. Table 1 shows the evaluation results of the obtained film.

(Example 5)
In Example 1, 1,3,5-triacryloylhexahydro-1,3,5-triazine was used instead of N, N′-ethylenebisacrylamide, and 45 parts of 2-acrylamido-2-methylpropanesulfonic acid was added to 35 parts. An electrolyte membrane was obtained in the same manner as in Example 1 except that 10 parts of acrylic acid was newly added. Table 1 shows the evaluation results of the obtained film.

(Example 6)
An electrolyte membrane was obtained in the same manner as in Example 1 except that 45 parts of 2-acrylamido-2-methylpropanesulfonic acid and 10 parts of N, N′-ethylenebisacrylamide were changed to 10 parts in Example 1. . Table 1 shows the evaluation results of the obtained film.

(Example 7)
In Example 5, 25 parts 2-acrylamido-2-methylpropanesulfonic acid, 25 parts, 10 parts 1,3,5-triacryloylhexahydro-1,3,5-triazine, 10 parts, 15 parts acrylic acid, 15 parts An electrolyte membrane was obtained in the same manner as in Example 3 except that the content of the electrolyte membrane was changed. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 1)
An electrolyte membrane was obtained in the same manner as in Example 1 except that N, N′-methylenebisacrylamide was used instead of N, N′-ethylenebisacrylamide in Example 1. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 2)
An experiment was carried out in the same manner as in Example 4 except that N, N′-methylenebisacrylamide was used instead of N, N′-ethylenebisacrylamide in Example 6, and it was not dissolved in the monomer solution. A large amount of N, N′-methylenebisacrylamide remained, making it difficult to fill the monomer substrate with the porous substrate, and an electrolyte membrane could not be obtained.

(Comparative Example 3)
An electrolyte membrane was obtained in the same manner as in Example 3 except that N, N′-methylenebisacrylamide was used instead of 1,3,5-triacryloylhexahydro-1,3,5-triazine in Example 5. . Table 1 shows the evaluation results of the obtained film.

(Comparative Example 4)
An electrolyte membrane was obtained in the same manner as in Example 1 except that N, N′-methylenebisacrylamide was used instead of 1,3,5-triacryloylhexahydro-1,3,5-triazine in Example 7. . Table 1 shows the evaluation results of the obtained film.

(Comparative Example 5)
In Example 6, instead of N, N′-ethylenebisacrylamide, 2 parts of N, N′-methylenebisacrylamide and 8 parts of N-methylolacrylamide were used, and after UV polymerization in the same manner as in Example 1, 120 ° C. And heated for 30 minutes to cross-link the methylol site of the N-methylolacrylamide residue to obtain an electrolyte membrane. Table 1 shows the evaluation results of the obtained film.

(Example 8)
In order to confirm that the obtained membrane functions as a fuel cell, the membrane prepared in Example 1 was incorporated into a DMFC cell and evaluated.
Platinum-supported carbon (Tanaka Kikinzoku Co., Ltd .: TEC10E50E) is used for the oxygen electrode, and platinum ruthenium alloy-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd .: TEC61E54) is used for the fuel electrode. A molecular electrolyte solution (manufactured by DuPont: Nafion 5% solution) and polytetrafluoroethylene dispersion were blended, and water was appropriately added and stirred to obtain a reaction layer coating material. This was printed on one side of carbon paper (manufactured by Toray Industries, Inc .: TGP-H-060) by screen printing and dried to obtain an electrode. At that time, the platinum amount on the oxygen electrode side was 1 mg / cm ² , and the total amount of platinum and ruthenium on the fuel electrode side was 3 mg / cm ² . These were superposed on the center of the electrolyte membrane obtained in Example 1 with the paint surface inside, and heated and pressed at 120 ° C. to prepare a membrane electrode assembly (MEA) for fuel cells. This was installed in a DMFC single cell and operated to confirm the performance. The DMFC operating conditions were such that the cell temperature was 50 ° C., a methanol aqueous solution having a concentration of 3 mol / liter was supplied to the fuel electrode at 10 ml / min, and pure air was supplied to the oxygen electrode at 0.3 liter / min. The voltage was read while increasing the current value, and the current density-voltage curve of FIG. 1 was obtained.

  As can be seen from Table 1, the Examples exhibited better performance in the durability test than the Comparative Examples.

  The electrolyte membrane of the present invention can be applied not only to fuel cells, but also to electrochemical device elements such as various sensors and separation membranes for electrolysis.

10 is a graph showing a current density-voltage curve in the fuel cell of Example 8.

Claims (10)

(A) a compound having a carbon-carbon double bond polymerizable in one molecule and a sulfonic acid group or a salt thereof, and (b) an acrylamide derivative and / or a methacrylamide derivative represented by the following structural formula (1)

R ₁ and R ₃ are hydrogen or methyl group
R ₂ is an alkylene group constituting a part of a chain or ring structure, and in the case of a chain, has 2 or more carbon atoms, and in the case of a part of the ring structure, R ₂ has 1 or more carbon atoms.
R ₄ and R ₅ each contain a crosslinked electrolyte polymer containing hydrogen, an alkyl group, or an alkylene group constituting a part of a ring structure as an essential constituent monomer. Monomer (b) is N, N′-ethylenebisacrylamide, N, N′-ethylenebismethacrylamide, N, N′-propylenebisacrylamide, N, N′-propylenebismethacrylamide, N, N′-butylene Bisacrylamide, N, N′-butylenebismethacrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, 1,3,5-trimethacryloylhexahydro-1,3,5-triazine The electrolyte membrane according to claim 1, wherein the electrolyte membrane is one or more compounds selected from bisacryloylpiperazine and bismethacryloylpiperazine. 2. The electrolyte membrane according to claim 1, wherein the monomer (b) is N, N'-ethylenebisacrylamide and / or N, N'-ethylenebismethacrylamide. 4. The electrolyte according to claim 1, wherein the monomer (a) is 2-acrylamido-2-methylpropanesulfonic acid and / or 2-methacrylamide-2-methylpropanesulfonic acid, or a salt thereof. film. The ratio of the monomers (a) and (b) to the total monomers constituting the crosslinked electrolyte polymer is 25 to 99.9% by mass and 0.1 to 75% by mass, respectively. The electrolyte membrane described. 5. The electrolyte membrane according to claim 1, wherein the ratios of the monomers (a) and (b) to the total monomers constituting the crosslinked electrolyte polymer are 40 to 90 mass% and 10 to 60 mass%, respectively. . 7. The electrolyte membrane according to claim 1, wherein the crosslinked electrolyte polymer is filled in pores of the porous substrate. The electrolyte membrane according to claim 1, which is obtained by a production method including the following steps.
(1) A step of filling a monomer constituting the crosslinked electrolyte polymer or a solution or dispersion thereof into the pores of the porous substrate.
(2) A step of polymerizing and crosslinking the filled monomer. 9. The electrolyte membrane according to claim 8, wherein the step of polymerizing and crosslinking the filled monomer is performed by ultraviolet irradiation. A fuel cell incorporating the electrolyte membrane according to claim 1.

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